Here's a photo tour of Muga, in Haro, Rioja, where I visited with some friends in October 2017. The winery is seriously impressive. The sheer number of coopers working in the barrel manufacturing area must be tough for anyone to surpass. I've been to wineries in Bordeaux where one or two coopers work there, but to have eight (if memory serves me right) experts working in that area must be more or less unrivalled anywhere in the world.
Jorge Muga was a thoughtful and insightful host, explaining that given the size of Muga's operations, and Tempranillo's important relationship with oak, he's able to take his wood very seriously indeed. At Muga they select the trees in the European forests, or at least the areas of forest (I think the former) years, and I mean years, before they are harvested, then take great interest in how the wood is aged, until it's delivered, where they make some of their own barrels (barriques more than the larger) to exactly the specifications they need.
I've been to a fair few wineries, but never seen an operation and attention to oak like this, with such long term planning and direct traceability. Seriously impressive, as are the wines. Check the links in this post or the photos below if viewing online, for a bit of a tour and to see the wines we tasted. And yes the wines were superb, and age beautifully. The 1991 in particular, is one of the best five wines I've had from the region.